Walters Scientific Instrument Labs (WSIL) is an integral partner in a collaborative effort to develop a clinically effective intravenous membrane oxygenator (IMO) which is intended to augment the incomplete respiration of patients with adult respiratory distress syndrome (ARDS). WSIL has worked with the University of Pittsburgh and Electromedics, Inc., since 1990 and more recently with the University of Texas Medical Branch, to design, fabricate and test a novel prototype IMO. The device is intended to reside in the inferior vena cava, right atrium, and superior vena cava, and incorporates hollow fiber membranes which are arranged around a centrally positioned balloon. The balloon is actuated pneumatically to pulse in a rhythmic fashion and actively mixes the native blood flow around the hollow fibers of the device. It is our hypothesis that the pulsation of the balloon induces three dimensional convective mixing around the hollow fibers and thereby promotes effective gas transfer. This hypothesis was carefully tested in vitro under an SBIR Phase l award to Electromedics. WSIL fabricated several series of prototype devices with design collaboration from program partners at the University of Pittsburgh and Electromedics. In vitro studies documented that the operation of the balloon at frequencies between 60 and 120 beats per minute improved blood oxygenation and decarbonation by a factor of 2.5-10 versus the static situation of no balloon pulsation. These studies also demonstrated that mass transfer for our device was superior by a factor of 2-2.5 to the intravascular oxygenator (IVOX, Cardiopulmonics, Inc., Salt Lake City, UT) which recently underwent Phase I and Phase II clinical trials. Other highlights of our IMO work to date include both acceptably low levels of hemolysis and low pressure drop for several prototypes, and an absence of fiber fracture in all IMO devices. Based on these encouraging results, a Phase II SBIR application was submitted to NIH on December 15, 1993. However, in April 1994, Electromedics, Inc. merged with Medtronic, Inc. and became ineligible for the SBIR program. Electromedics and Medtronic have endorsed and encouraged the transfer of the Phase II SBIR to Walters Scientific Instrument Labs which has been a significant contributor to this development project. WSIL is a small business that has been active in technology transfer and development projects with the University of Pittsburgh in addition to a number of other research institutions and is well qualified to undertake this research effort.